Effects of Different Sallow Water Acoustic Channel Models on Error-correction Code Performance Analysis

由于水声信道复杂多变,很难进行信道建模,迄今为止并没有一个标准的统计信道模型。针对不同的研究对象,往往需要采用不同的水声信道模型,而评估信道建模差异对研究结论的影响则具有重要意义。从信道纠错码角度,在分析时不变信道模型、时变信道模型和准静止衰落信道模型的基础上,结合高效信道纠错码(以ldPC码为例),讨论了水声信道模型差异对研究纠错码性能可能带来的影响,为实际设计水声通信系统提供参考。仿真结果表明,尽管不同信道建模方式对系统解码的具体信噪比数值要求不大相同,但编译码参数优化设计的方案基本一致,海试数据则进一步验证了上述结论。There have been no standard statistical channel models for the underwater acoustic( UWA)channel as a result of the complex and variability of UWA channel.Different UWA channel models are required for different purposes during the UWA communication research.It is important to evaluate the effect of different UWA channel modeling on research conclusions.From the perspective of channel errorcorrection code,the effects of different channel models on channel error-correction code( taking LDPC codes as an example) design are investigated by analyzing several UWA channel models,including timeinvariance model,time-variance model and quasi-static fading model adopted in UWA communication simulation.The simulation results show that the optimized designs of coding parameters are almost the same,although different channel modeling usually requires different signal-to-noise ratio for decoding.The sea test data are adopted to further verify the conclusions.国家自然科学基金项目(41176032、41376040); 中央高校基本科研业务费专项基金; 厦门大学基础创新科研基金项目(201112G020、201212G012); 高等学校博士学科点专项科研基金项目(20130121120033

激光作用产生离子引发的苯乙烯聚合

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The Wandering Soul and the Guardian Spirit:Why I Was Converted to Anthropology?

人作为一种哺乳动物 ,不管有着怎样的生物性、动物性 ,但毕竟具有文化性、社会性的特征。因此 ,无论有过怎样的心灵漂泊 ,兰林友先生始终守望着他的精神家园。如若剖析人之所以为人 ,人类学便成为他的监护精灵和必修功课。因为无论人类学的学科性质有着怎样的争议 ,但人类学终究是研究活生生的人———其文化与人性———的学

Reflections on Chinese Discourse of Anthropology——Interviewing Doctor LAN Lin-you, a Visiting Scholar of Harvard University

中国在一定程度上早已关注到中国社会到底是怎样,即中国也有自己的话语资源。中国有五千年的文化积累,中国学者应从中国的背景、中国的材料出发,寻求历史资源作为人类学中国话语的最初源头,构建出人类学的中国话语。人类学的中国话语必须遵循两个原则:一是不能盲目排外,二是在此基础上要有自信,这样,建立人类学的中国话语才能丰富世界人类学的宝库。 To some extents, China began to concern with what the Chinese society would be like in the earlier times, which means that China has its own discourse resources. By searching for its historical origins on the basis of Chinese background and available data with a long history of accumulated culture, Chinese scholars construct the discourse resources of anthropology, which are meant to follow two rules——not excluding any foreign culture blindly and being confident. Only in this way can the established anthropological Chinese discourse bring more values to the world＇s anthropology

Applications of rate-compatible QC-LDPC codes in underwater acoustic communication

针对水声信道复杂多变、强多途和大起伏干扰等特点,提出采用码率兼容QC-ldPC码的自适应信道编码技术,以提高水声数据传输的可靠性和水声信道的信道吞吐率。建立了码率兼容QC-ldPC码在水声信道中的仿真模型,构造码率为1/2、2/3…5/6等一系列QC-ldPC码,在三种典型的水声信道中对其性能进行仿真。结果表明所设计的码率兼容QC-ldPC码在三种不同信道下可行有效,能较大地提高水声通信系统的性能。由于信道时延越长、信噪比越低,满足通信指标的码率就越低;并给出码率兼容QC-ldPC码在浅海水声信道中不同信噪比下满足通信性能指标的编码码率的查找表。码率兼容QC-ldPC码提高了水声通信的信道利用率,具有灵活的编译码性能,在水声自适应通信中具有很好的应用前景。The underwater acoustic(UWA) channel is characterized as a complex variable, strong multipath and fluctuation interference channel.Adaptive channel coding techniques which use rate-compatible QC-LDPC(RC QC-LDPC) codes are proposed to enhance the reliability of UWA data transmission and channel throughput.A system simulation model including RC QC-LDPC codes for the UWA channels is built.With constructing a series code-rates(such as 1/2, 2/3, …, 5/6) of QC-LDPC codes, the performance of the system is simulated over three different kinds of UWA channels.The simulation results show that the designed RC QC-LDPC codes are feasible and effective, can dramatically improve the performance of UWA communication system, have good applicability in UWA channels.In the case that the worse the channel, due to longer channel delay and lower signal-to-noise ratio, the lower the code-rate is taken to meet system communication indicators.The lookup table(LUT) of the rate compatible QC-LDPC codes, which meet the communication indicators of the shallow water acoustic communication system under different signal-to-noise ratios, is given.The RC QC-LDPC codes with flexible encoding and decoding performances can improve the utilization of UWA communication channel and have good application prospects.国家自然科学基金(41176032、41376040)资助项

Irregular QC-LDPC Coding Joint Adaptive Equalization for Shallow Water Acoustic Communications

浅海水声信道具有长时延、多途强、起伏快等特点,为提高数据传输可靠性,采用纠错能力强、编译码复杂度低的非规则准循环低密度奇偶校验(QC-ldPC)码作为信道纠错码方案,并联合自适应判决反馈均衡器(dfE)作为接收机结构以消除码间干扰(ISI).综合考虑非规则QC-ldPC码编译码参数选择、自适应均衡器中的最小均方差(lMS)、可变步长lMS(SVSlMS)和递归最小二乘(rlS)等3种算法的性能与复杂度权衡问题,结合福建泉港浅海域实测水声信道特性,研究了该接收机的性能.仿真结果表明:非规则QC-ldPC码的性能优于随机构造的规则ldPC码;联合自适应均衡的非规则QC-ldPC码可显著提高浅海水声通信系统性能,在较高信噪比(Snr)下,选用rlS算法时,误码率(bEr)可降为0(15db),选用低复杂度的SVSlMS算法bEr可达到10-4(18db).Shallow water acoustic channel is characterized by long transmission delay,strong multipath interference,and large fluctuation.To improve reliability of underwater acoustic data transmission,this paper use irregular quasi-cyclic low density parity check(QC-LDPC)codes as an error-correcting coding scheme,which have strong error correction capability and low coding and decoding complexity,joint adaptive equalization as a receiver structure for eliminating inter-symbol interference caused by strong multipath effect.This paper makes comprehensive considerations of optimal design problem,such as the choices of coding and decoding parameters for irregular QC-LDPC codes,the balances of performance and complexity for least mean square,recursive least squares and sigmoid variable step-size least mean square algorithms in adaptive decision feedback equalizer;combining the measurement shallow water acoustic channel of characteristics Fujian quangang Xiaocuo harbour to analyses the performance of the receiver.Simulation results show that the irregular QC-LDPC codes perform better than random structure regular LDPC codes;irregular QC-LDPC coding joint adaptive equalization can significantly improve the performance of shallow water acoustic communication system.At high SNR,when select RLS algorithm,bit error rate can be reduced to 0;when select SVSLMS algorithm with low complexity,error rate can reach 10-4.国家自然科学基金(41176032;41376040

第四论坛会议摘要

主题:汉人社会研究的范式、进展和启示时间:2003年10月8日16:10—18:00报告人及主讲内容廖迪生(香港科技大学教授)

亲社会风险行为及其理论模型与神经机制

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丙烯腈和丙烯酸酯基团转移共聚的竞聚率

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